F. C. Buchanan

Association of a missense mutation in the bovine leptin gene with carcass fat content and leptin mRNA levels

Previously, we have shown that alleles of the BM1500 microsatellite, located 3.6 kb downstream of the leptin gene in cattle, were associated with carcass fat measures in a population of 154 unrelated beef bulls. Subsequently, a cytosine (C) to thymine (T) transition that encoded an amino acid change of an arginine to a cysteine was identified in exon 2 of the leptin gene. A PCR-RFLP was designed and allele frequencies in four beef breeds were correlated with levels of carcass fat. The T allele was associated with fatter carcasses and the C allele with leaner carcasses. The frequencies of the SNP alleles among breeds indicated that British breeds have a higher frequency of the T allele whereas the continental breeds have a higher occurrence of the C allele. A ribonuclease protection assay was developed to quantify leptin mRNA in a separate group of animals selected by genotype. Animals homozygous for thymine expressed higher levels of leptin mRNA. This may suggest that the T allele, which adds an extra cysteine to the protein, imparts a partial loss of biological function and hence could be the causative mutation.

A missense mutation in the bovine MGF gene is associated with the roan phenotype in Belgian Blue and Shorthorn cattle

Abstract. The Roan locus is responsible for the coat coloration of Belgian Blue and Shorthorn cattle. The solid-colored and white animals are homozygotes, and the roan animals, with intermingled colored and white hairs, are heterozygous. The roan phenotype was mapped to cattle Chromosome (Chr) 5 with microsatellites, and a candidate gene was proposed (Charlier et al. Mamm Genome 7, 138, 1996). PCR primers to the exons of this candidate gene, the steel locus or mast cell growth factor (MGF) were designed. Solid-colored and white animals were sequenced. A missense mutation at 654 bp (amino acid 193, Ala → Asp) was detected in these two groups. A PCR-RFLP was designed to this single base pair change, and 143 animals in total (Belgian Blue, Shorthorn, and various other breeds) were screened. In addition, the Canadian Beef Cattle Reference Herd (http://skyway.usask.ca/∼schmutz) was used to verify Mendelian inheritance of this marker with the phenotypic inheritance of roan. Our data suggest that this mutation in the bovine MGF gene is responsible for the roan phenotype.

Development of the Canadian beef reference herd for gene mapping studies

A project to map quantitative trait loci (QTL), in beef cattle using a full-sib design was initiated using six Bos taurus breeds. Embryo transfer was used in a large scale, short timeframe experiment to develop this herd for gene mapping. Full-sib families allowed for genetic information to be followed through both the sire and the dam and for both parents to be slaughtered so that carcass quality data could also be obtained from both of them at close to typical slaughter ages. Repeatability of response to superovulation was significant among the 3 flushes per female. Response to superovulation was negatively correlated with backfat of the donor. Crossbred embryos were found to have higher survival than purebred embryos.

Genetic diversity and admixture among Canadian, Mountain and Moorland and Nordic pony populations

As part of the requirements of the Convention on Biological Diversity, Canada has been investigating the genetic diversity of its native equine and pony populations. Along with examining four indigenous Canadian equine populations (Canadian horse, Lac La Croix pony, Newfoundland pony and Sable Island population), another 10 Mountain and Moorland, three Nordic, four horse and two feral equine populations (thought to have influenced some pony breeds) were also investigated. In total, 821 individuals were genotyped at 38 microsatellite loci. Results of the analysis of molecular variance indicated that 13.3% of genetic diversity was explained by breed differences, whereas 84.6% and 2.1% of diversity came from within and among individuals, respectively. The average effective number of alleles and allelic richness was the lowest in the Eriskay (2.51 and 3.98) and Lac La Croix (2.83 and 4.01) populations, whereas it was highest in the New Forest (4.31 and 6.01) and Welsh (4.33 and 5.87) breeds, followed closely by the Newfoundland-CDN (4.23 and 5.86) population. Expected heterozygosities varied from 0.61 in the Lac La Croix to 0.74 in the Welsh and in Newfoundland. Observed heterozygosities ranged from 0.57 in the Exmoor and 0.58 in the Sable Island herd to 0.77 in the Kerry Bog and 0.76 in the New Forest breeds. Structure and admixture analyses revealed that the most likely number of clusters was 21, although some substructure was also observed when K = 16, compared with the 24 predefined populations. Information gathered from this study should be combined with other available phenotypic and pedigree data to develop, or amend, a suitable conservation strategy for all populations examined.

Temperament in beef cattle: Methods of measurement and their relationship to production

Sebastian, T., Watts, J. M., Stookey, J. M., Buchanan, F. and Waldner, C. 2011. Temperament in beef cattle: methods of measurement and their relationship to production. Can. J. Anim. Sci. 91: 557-565. Temperament is an individual trait influencing an animals behavioural response to handling. This characteristic likely modulates the response of the animal to environments and social situations, and is perhaps best viewed as a component of its personality. We assessed temperament using three objective measuring tools, to determine if correlations exist between these and a traditional subjective evaluation. The tools used were strain gauges, a “movement measuring device” (MMD), and a chute exit timer. Four hundred steers were used. Exit time was correlated with values recorded with the MMD and absolute strain forces, and MMD values were related to absolute strain forces. When the animals were classified as “calm” or “wild” based on their subjective scoring, these two groups differed in their mean exit times, MMD values and absolute strain forces. The three objective measures yielded statistically correlated results between tests and across repetitions, and therefore may quantify correlated aspects of a personality trait (i.e., temperament). The objective scores were related to the traditional subjective score, but they provide the advantage of eliminating observer bias and may offer better tools for temperament selection. Significant positive relationships of daily gain with subjective score and MMD values indicate that traditional subjective scoring techniques can be replaced with more repeatable objective measures when temperaments are assessed for performance studies.

The impact of vitamin A restriction and ADH1C genotype on marbling in feedlot steers.

A novel SNP was discovered within the promoter region of alcohol dehydrogenase 1C (ADH1C c.-64T>C), the C allele eliminating a potential binding site for the transcription factor C/EPBα. The purpose of this study was to examine if an interaction between this SNP and vitamin A restriction had an effect on carcass characteristics in beef cattle. Following backgrounding on a β-carotene-deficient diet, 130 steers (50 TT, 50 CT, and 30 CC) were finished for 5 mo and received either no supplemental vitamin A (unsupplemented) or 750,000 IU/mo (supplemented). A subgroup of 5 steers • genotype(-1) • treatment(-1) was randomly selected for pre- and postfinishing liver biopsies to assess vitamin A status and measure gene expression. Unsupplemented steers (Bos taurus) had significantly greater (P < 0.05) marbling scores than supplemented steers. There was a significant interaction between genotype and vitamin A supplementation on ether-extractable intramuscular fat (IMF). Within the unsupplemented treatment, TT steers had nearly 23% greater IMF than CC steers. Additionally, unsupplemented TT steers had over 24% greater IMF than supplemented TT steers. Expression of ADH1C in the liver was additive with each additional T allele, potentially due to the elimination of a possible binding site for C/EBPα. It is plausible that CC cattle have reduced ability to metabolize retinol to retinaldehyde (and subsequently retinoic acid) and that a phenotypic effect is only observed when vitamin A is limiting. Therefore, ADH1C c.-64T>C genotype, in combination with reduced vitamin A supplementation, could potentially be implemented in marker-assisted management to maximize marbling in finishing cattle.

The leptin arg25cys affects performance, carcass traits and serum leptin concentrations in beef cattle

A single nucleotide polymorphism (SNP) in the bovine leptin gene has been associated with carcass traits and elevated gene expression. To examine the relationship between leptin genotype with serum leptin concentration and carcass traits, blood samples were collected 24 h prior to slaughter in 89 head of cattle. Cattle were predominantly of Angus (n = 26), Hereford (n = 31) and Charolais (n = 32) breed types with approximately half homozygous for the T allele or the C allele. Cattle were limit fed to achieve 1 kg d-1 liveweight gain for a 70-d background period while during finishing, animals were fed ad libitum such that half the animals within each breed type were slaughtered at 8 or 12 mm back fat determined by ultrasound. Preslaughter serum leptin and insulin were determined using radioimmunoassays (RIA) specific for cattle and sheep. Animals homozygous for the T allele had greater (P < 0.05) backfat depth at the beginning (2.4 ± 0.49 vs. 1.8 ± 0.49 mm) and end (3.1 ± 0.42 vs. 2.4 ± 0.42 mm) of the ba...

Intrabreed polymorphic information content of microsatellites in cattle and sheep

Eight ovine and eleven bovine microsatellites were amplified in unrelated individuals from five breeds of sheep and cattle respectively. Polymorphic information content (PIC) was calculated for each breed. It was shown that the common practice of using genotypes from several breeds to calculate PIC for a livestock species can give misleading PIC values for a given breed. Key words: Microsatellite, polymorphic information content

Characterization of two Pro-opiomelanocortin gene variants and their effects on carcass traits in beef cattle

BackgroundCarcass quantity (lean meat yield) and quality (degree of marbling) in beef cattle determines much of their economic value. Consequently, it is important to study genes that are part of the appetite pathway and that may ultimately affect carcass composition. Pro-opiomelanocortin is a prohormone that codes for many different peptides, several of which are involved in the appetite pathway. A single nucleotide polymorphism (SNP) c.288C>T in pro-opiomelanocortin (POMC) has previously been associated with hot carcass weight (HCW) and shipping weight (Ship wt) in beef cattle.ResultsWhile developing a commercial real time PCR test for POMC c.288C>T a 12 bp deletion (POMC c.293_304delTTGGGGGCGCGG) was identified. The deletion results in the removal of four amino acids (a valine, two glycines, and an alanine). Both the POMC c.288C>T and the deletion were genotyped in 386 crossbred steers and evaluated for associations with carcass traits. The animals with one copy of the deletion had a significantly smaller carcass rib-eye area (7.91 cm2; P = 0.02) in comparison to homozygous normal animals. Significant associations were observed between POMC c.288C>T with start-of-finishing weight (SOF WT; P = 0.04), hot carcass weight (HCW; P = 0.02), average fat and grade fat (both P = 0.05), carcass rib-eye area (REA; P = 0.03) and marbling (P = 0.02).ConclusionsThese results suggest that it could be beneficial for beef producers to know both the deletion and POMC c.288C>T genotypes when making marketing and culling decisions.

Effects of leptin Arg25Cys on peripheral mononuclear cell counts and antibody response to vaccination in beef cattle

A single nucleotide polymorphism (SNP) in the leptin gene that results in Arg25Cys has been associated with beef carcass quality and milk composition in dairy cattle. However, leptin (LEP) also plays a role in immune performance and hence it was important to determine whether selection based on this SNP would negatively affect immune cell numbers or antibody production. LEP c.73C>T was assessed for effects on immune cell counts and antibody titres in 27 beef cattle herds (n = 556). A commercial rabies vaccine had been administered to these animals. Prior to being vaccinated, counts of several important mononuclear cells (total and activated B lymphocytes, total and activated T helper and T cytotoxic, WC1 T lymphocytes and monocytes) as well as baseline serum antibody titres were determined for each animal. On day 21, antibody titres were measured and a booster vaccine was administered. Finally on day 42, antibody titres and mononuclear cell types were again counted. Counts of six different cell types were significantly associated with the LEP genotype; however, no consistent patterns were observed between LEP genotype (TT, CT or CC) and peripheral blood mononuclear cell populations. Significant differences in the production of rabies antibodies in response to vaccination were observed relative to LEP genotype. Our results suggest that selection for either the C or T allele would not detrimentally impact on the measured indicators of immune function in beef cattle.